使用 Java.util 的 Logger 和 FileHandler 类时，几秒钟后未更新日志文件 [英] Log File not being updated after few seconds while using Logger and FileHandler Class of Java.util

问题描述

我正在使用以下类LoggerUtil"来记录到控制台和文件logfile.log".记录到控制台工作正常.但是，记录到 'logfile.log' 文件会在几条日志后停止.欢迎任何有关定位错误的建议.我附上下面的代码:

I am using the following Class 'LoggerUtil' for logging to console and to a file 'logfile.log'. The logging to console is working fine. However, logging to 'logfile.log' file stops after few logs. Any suggestions in locating the bug would be welcome. I am attaching the code below:

public class LoggerUtil {   
  public static final String LOGGERNAME = "project.logging";

  static {
      try {
          Logger.getLogger(LOGGERNAME).setUseParentHandlers(false);
          Handler ch = new ConsoleHandler();
          Handler fh = new FileHandler("logfile.log");
          SimpleFormatter sf = new SimpleFormatter();
          fh.setFormatter(sf);
          Logger.getLogger(LOGGERNAME).addHandler(ch);
          Logger.getLogger(LOGGERNAME).addHandler(fh);
          setHandlersLevel(Level.ALL);
      } catch (IOException | SecurityException ex) {
          Logger.getLogger(LoggerUtil.class.getName()).log(Level.SEVERE, null, ex);
      }
  }

  public static void setHandlersLevel(Level level) {
      Handler[] handlers = Logger.getLogger(LOGGERNAME).getHandlers();
      for (Handler h : handlers) {
          h.setLevel(level);
      }
      Logger.getLogger(LOGGERNAME).setLevel(level);
  }

  public static Logger getLogger() {
      return Logger.getLogger(LOGGERNAME);
  }
}

我从项目中的各个地方调用以下代码进行记录:

I call the following code from various places in my project to log:

LoggerUtil.getLogger().log(Level.INFO, "Message to be logged");

请注意，我的项目是多线程的.不同的线程使用相同的文件进行日志记录.这可能是并发问题还是只是一个红鲱鱼！

Kindly note, my project is multithreaded. Various threads use the same file for logging. Could this be a concurrency issue or is that just a red herring!

推荐答案

硬引用您的记录器.经验法则是在类中使用静态 final 字段.

Make a hard reference to your logger. Rule of thumb is to use a static final field in your class.

public static final String LOGGERNAME = "project.logging";
//Pin logger in memory.
private static final Logger logger = Logger.getLogger(LOGGERNAME);

来自记录器.getLogger(String) 文档:

注意:LogManager 可能只保留对新创建的 Logger 的弱引用.重要的是要了解，如果没有对 Logger 的强引用，先前创建的具有给定名称的 Logger 可能会随时被垃圾回收.

Note: The LogManager may only retain a weak reference to the newly created Logger. It is important to understand that a previously created Logger with the given name may be garbage collected at any time if there is no strong reference to the Logger.

当记录器被垃圾收集时，您的 ConsoleHandler 和 FileHandler 不会重新附加到新的记录器.

When the logger is garbage collected your ConsoleHandler and FileHandler are not reattached to the new logger.

使用 FindBugs，因为它检测到此错误模式:

Use FindBugs because it detects this bug pattern:

LG:由于 OpenJDK 中的弱引用，记录器更改可能丢失 (LG_LOST_LOGGER_DUE_TO_WEAK_REFERENCE)

LG: Potential lost logger changes due to weak reference in OpenJDK (LG_LOST_LOGGER_DUE_TO_WEAK_REFERENCE)

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